TBH I'm in the USA so mostly use iMessage or SMS. I use WeChat to talk to some friends but I would not consider it secure at all. I have a special dislike for Zuckerberg so that's mostly my dislike for WhatsApp but likely any messenger app is secure enough for most conversations like can you pick up bread after work or planning to go out for the weekend. I would not feel they are secure enough for data like credit card numbers or conversations like I'm going to the bank at noon to withdraw a large sum of money.
I found this article and it seems to go over some points
Signal and Telegram each have their strong points and their weak points
www.tomsguide.com